Stress urinary incontinence (SUI) occurs when tissue supporting the pelvic floor no longer provides sufficient support to the bladder neck and urethra, particularly the proximal urethra. Because of this condition, the bladder pushes against the urethra. Pressure from the abdominal muscles (e.g. during such activities as laughing, sneezing, coughing, exercising or straining to lift objects) can then cause undesired urine emissions. Females whose pelvic floors have stretched due to, for example, childbirth, obesity, etc. are more likely to suffer from stress incontinence.
Several treatments for SUI are available, ranging from medications to surgical interventions. One minimally invasive treatment for SUI utilizes radio frequency (RF) energy delivered to tissue of the pelvic floor, specifically to the endopelvic fascia (EPF) which lies beneath the surface of the vaginal wall. The RF energy heats the tissue of the endopelvic fascia and causes the collagen in the tissue to denature, so that the fascia shrinks. When the fascia shrinks, it returns the bladder and urethra to a more natural position within the pelvis, reducing the symptoms of incontinence. Other types of energy may be used to heat the tissue, such as acoustic energy, laser energy, microwaves etc.
Procedures to treat the endopelvic fascia require the accurate placement of the energy source within the vaginal canal of the patient, to successfully heat the target tissue. More generally, there are many medical procedures where a probe or other ‘medical implement is inserted into a body lumen or cavity, to achieve some therapeutic effect on the surrounding tissue. In all these procedures, it is important to be able to accurately place the probe or other device relative to the target tissue, without direct visualization of the device. This task may be made difficult because of the geometry of the lumen, or because of the lack of convenient reference points near the opening of the lumen.